Handle comments in latest MAT release

### Notes ###
- updated Gemfile to point to health-data-standards/[<code>bonnie_master</code>](https://github.com/projectcypress/health-data-standards/tree/bonnie_master)
- added <code>comments</code> to precondition model
- removed usage of precondition.<code>push_down_comments()</code>, and set comments on the current precondition instance post-handling instead
- updated precondition.<code>push_down_comments()</code> to append comments
- fixed comment parsing in utilities.<code>comments_on()</code>
- resolved issues with tests